Artificial turf sports playing surfaces are becoming increasingly popular as a replacement for natural grass in stadiums, on golf courses, play ground areas and on sports playing fields. Artificial turf sports playing surfaces require less maintenance than grass surfaces, and do not require water, chemicals or sunlight for satisfactory performance and sustainability. The environmental impact of artificial sports surfaces is considered less than that of an equivalent grass sports surface, not least because of reduced water and maintenance requirements. The versatility of synthetic turf allows it to be placed in totally dry regions, regions of high rainfall, extreme heat conditions and cold regions. It requires no sunlight and can be laid indoors. It can even be made to be portable; laid and removed as and when needed for use.
Most synthetic grass materials are comprised of rows of grass-like polymer flat ribbons, strips, twisted yarns, fibrillated yarns, texturised yarns and like forms that are tufted and bonded into a synthetic backing material. Polypropylene and polyethelene polymers are almost always used. The polymer ribbons or strands stand vertically into the backing media, then fine granulated or ground particulate materials such as sand, polymer granules, ground or granulated rubber, polymer foam etc. are in-filled between the synthetic ribbons to support the vertical oriented ribbons and also provide impact cushioning for player comfort and safety where needed.
The synthetic ribbons for example are inserted into the backing media normally by a tufting process. The backing media is then normally coated or covered by a bonding compound to prevent removal of the polymer ribbons from the backing material. The polymer ribbons act like grass and usually extend above the level of granular infill so that the ribbons simulate the aesthetic characteristics, and to some degree behaviour, of natural grass. The length of the ribbons above the infill surface is provided according to the end use of the playing surface. By way of example, longer pile lengths are desirable for football and baseball fields compared to shorter pile lengths required for tennis, golf and bowls.
Compared to football, American football and rugby, games such as tennis, croquet, hoop ball, golf and bowls require a playing surface which provides greater ball roll precision and predictability. Greater ball roll precision and predictability enhances the effect of differing skill levels of the players. Within these latter sports, the smaller ball size and degree of contact of the ball with the playing surface also require consistent and predictable rolling speed and directional stability. Currently, synthetic playing surfaces using in-fill technology are commonly used, however, the non-uniformity of the synthetic sports surface and the infill materials negatively impact upon the predictability of the rolling speed and directional stability of the ball. Artificial surfaces using infill also require considerable maintenance to achieve a reasonable degree of playing consistency. Also, importantly, artificial surface using infill may have a significant negative impact on the play of a competitive game because the artificial surface may adversely affect the roll of the ball compared to a natural turf surface.
Still other versions of prior art artificial grass have been developed using non-tufting technology. This design development has successfully eliminated the need for in-fill materials; however, the technology still relies upon traditional polymeric make-up of the artificial grass such as polypropylene and polyethylene and chemical binders or bonding solutions to provide the integrity of the synthetic grass surface. While this material make-up and construction provides some improvement over in-fill technology, such surfaces are susceptible to negative influences due to minor climatic change. The games for targeted use are normally played outdoors, where climatic conditions may vary minute by minute, so it is undesirable for such variations to greatly influence the performance of the synthetic surface. Use of a playing surface with characteristics which change rapidly during play reduces predictability and increases the extent to which player competition is left to chance, which is highly undesirable.
The present inventors have discerned that polymers and chemical binding solutions used in non-infill artificial playing surfaces can rapidly change in hardness when exposed to variable temperatures from direct sunlight to shaded zones. This thermal change affects the hardness properties of the synthetic playing surface, ball friction and ball tracking characteristics. Also, polyolefin polymers, such as polypropylene and polyethylene fibres are used as the synthetic sport surface in contact with the ball or within the fibre matrix. These polymers generally become soft with heat which changes the friction properties between the ball and the synthetic surface. By way of example, ball speed in areas of such a synthetic surface that are exposed to direct sunlight may be slower compared to areas on the same synthetic playing surface that are in shade. These polymers and polymer binders react quickly to thermal changes, meaning the ball speed can change rapidly, making luck or chance an increased factor in game results. Still further complexities are introduced by moisture, whereby rain, water seepage, dew etc is adsorbed into the synthetic fibre matrix and polymer binders, resulting in different playing characteristics in different regions of the artificial playing surface and at different times during a game.
It is, therefore, highly desirable to produce an artificial grass playing surface having improved resistance to climatic influence, thus, allowing for greater opportunity for player skill to determine the outcome of competition, particularly at professional and international competition playing levels. These improvements are required for many types of sport playing surfaces including, but not limited to golf and bowls where predictability of ball speed and line of direction are paramount. Simulation or replication of the properties of natural grass is one of the objectives for performance based synthetic sports surfaces and a high degree of predictability is the desired outcome.
It would be desirable for at least embodiments in accordance with the present disclosure to overcome one or more of these disadvantages, or at least to provide a useful alternative.